WASHINGTON – It appears that just being glad you have a job isn’t enough for most people anymore.

A new survey by the Conference Board has found that only 45 percent of Americans are satisfied with their work, the lowest level recorded in more than two decades of polling by the New York-based research group. Unhappiness is growing among Americans of all ages and income brackets.

The rate of worker satisfaction has fallen steadily from the high of 61 percent recorded when the survey began in 1987. It fell to 51 percent in 2000 but ticked up to 52 percent in 2005 before falling to 45 percent in the latest poll.

The reasons Americans gave for being unsatisfied with their jobs included their pay failing to keep up with inflation; the rising cost of health insurance; and finding their work uninteresting.

Among different age groups, young workers under the age of 25 were the least happy about their jobs, with just 36 percent describing themselves as satisfied, down from 56 percent in 1987. The most satisfied workers were those ages 25 to 34 and those ages 45 to 54, both at 47 percent.

Only 51 percent of the 5,000 households surveyed said they find their jobs interesting, another record low. In 1987, almost 70 percent reported being interested in their work.

“It says something troubling about work in America. It is not about the business cycle or one grumpy generation,” Linda Barrington, managing director of human capital at the Conference Board, told The Associated Press.

She noted that baby boomers, who will make up one-quarter of workers in eight years, have been “increasingly losing faith in the workplace” since the late 1980s.

“The growing dissatisfaction across and between generations is important to address because it can directly impact the quality of multi-generational knowledge transfer – which is increasingly critical to effective workplace functioning,” she said in a news release.

Lynn Franco, director of the Conference Board’s Consumer Research Center, said the results are a bad omen for the nation’s long-term economic prospects. “The downward trend in job satisfaction could spell trouble for the overall engagement of U.S. employees and ultimately employee productivity,” she said.